1. Field of the Invention
The present invention relates, generally, to the field of printing press systems and, more particularly, to improved paper perforating and scoring devices for use with continuous web printing presses.
2. Prior Art
Expensive, high speed printing presses are commonly used by commercial printing companies. Many such printing presses are fed from large rolls of paper, in a continuous strip known in the art as a "web". The presses are generally known in the industry as web presses and may cost millions of dollars each.
Typically, a web press requires the use of an automated web cutting and folding machine to receive the printed web at high velocity. The cutting and folding machine automatically cuts the web into sheets and folds the sheets into "signatures". The signatures may be sold as produced or they may be delivered to other machines which bind the signatures into books, magazines, or the like.
It can be appreciated that the presses and folding machines must be capable of operating for extended periods of time at very high speeds in order to be cost effective in the production of finished signatures.
Many commonly used signature folders are constructed to perform two or more sequential paper folding operations. The first folding stage is typical inasmuch as the web is still intact and taut when the first fold is made. However, any subsequent fold (which can be repeated several times) is, generally, accomplished by a blade striking the severed sheet along a second fold line and pushing the new fold between a second (and subsequent) pair of rollers.
To avoid the use of two separate signature folders, each of which is operated at half the press speed, press and folder manufacturers have attempted to reduce the second stage folding problems by scoring the web along the second fold line before the first fold is made. For such pre-fold scoring, the web passes through a web scoring apparatus in the signature folder upstream of the first folding stage. The scoring apparatus, typically, includes a circular scoring blade mounted on one side of the web and a resilient roller mounted on the other side of the web. As the web advances between the rotating scoring blade and roller, the blade presses a longitudinal indentation or groove into the web along the subsequent second fold line.
The web is scored in alternating directions. Such a device is referred to as a "skip-scorer" and is described in U.S. Pat. No. 4,524,962.
The skip-scorer of the prior art includes first and second rollers each having separate scoring and resilient abutment portions to score the paper web in alternating directions. The scoring means are mounted in the path of paper travel so as to enable scoring of the paper before the paper enters the first folding stage.
The known scoring means comprise first and second complementary-shaped scoring rollers, each of which has alternating peripheral scoring blades and resilient roller portions having arc lengths equal to the length of the fold. The first and second scoring rollers are, typically, rotatably mounted upstream of the first folding stage and in the path of paper web travel. The scoring rollers are mounted in mutual, peripheral rolling contact so that the respective scoring blade contacts the respective resilient roller portion (or anvil) of the other as the scoring rollers are rotated. Portions of the paper passing between the scoring rollers are thereby scored in one direction and other portions of the paper are scored in the opposite direction so that each layer of paper is scored in the correct folding direction.
However, this operation tends to cause the resilient portion of the rollers to wear down. When the resilient portions wear down, the scoring does not occur accurately. Thus, it is necessary to replace the resilient portion of the roller. This replacement is time consuming and expensive in that the roller must be removed from the press and a new roller inserted. The technique is, generally, not satisfactory
A more economical arrangement for scoring and/or perforating is described in U.S. Pat. No. 5,045,045 of H. Davenport et al. In this apparatus, the scorer and/or perforator includes a blade bolted to a semi-circular hub or support which is bolted to the roller. The anvil is a resilient, T-shaped strip which is embedded in a T-shaped slot in a semi-circular hub or support. The anvil support and the blade support are bolted to each other and clamped to the drive shaft. In this apparatus, replacement of a worn anvil strip is simplified. That is, the anvil support is removed from the shaft. The worn T-shaped resilient strip is removed and replaced by a new strip. The hub or support is then bolted into place. This entire process is quicker, easier and less expensive than that in the prior art. Nevertheless, improved desived are still desirable.